misterhouse-users

I'm presently running my doorbell button through an old northern RFID
panel but I'm planning on replacing that system with a more modern RFID
setup (http://www.apsx.com/RW210.aspx)
But, I'll lose my various input ports that are on the old unit.
What's the current tech for getting single bits into misterhouse?
A friend has weeder but thinks it's probably not the best solution out
there.
Cost effective would be nice too. :)
Thanks
Greg